1. Field of the Invention
The present invention relates to an electrooptical display apparatus such as a liquid crystal display apparatus that displays images by electrooptical change.
2. Description of the Related Art
A drive circuit of such an electrooptical display apparatus is disclosed in Japanese Patent No. 3367808 which, in a period of time where a selection voltage is applied to a scan line, maintains a voltage applied to a common electrode constant and applies a signal (pixel voltage) that monotonously changes to a pixel electrode through a switch turned on and a data line. The drive circuit turns the switch off after elapse of a time corresponding to a target gradation (input gradation) to holds a voltage difference between the pixel electrode and the common electrode.
However, when using the drive circuit disclosed in Japanese Patent No. 3367808, if the pixel voltage does not monotonously change according to its setting for some reason, the voltage difference between the pixel electrode and the common electrode corresponding to the target gradation cannot be obtained, which makes it impossible to display the target gradation and thereby deteriorates image display quality.
As a countermeasure for such a problem, Japanese Patent Laid-Open No. 2008-170843 discloses a drive circuit that absorbs noise generated in the pixel voltage, which should monotonously change, due to variation of load (capacitance) during application of the pixel voltage. This drive circuit connects a load different from the load during the application of the pixel voltage to a voltage supply line or a common electrode in response to the load variation, and thereby suppresses the variation of the load, that is, variation of the pixel voltage, which prevents the reduction of the image display quality.
However, when using the drive circuit disclosed in Japanese Patent Laid-Open No. 2008-170843, if the load connected to the voltage supply line or the common electrode in order to suppress the load variation (pixel voltage variation) is an external load, a sufficient effect cannot be obtained for the load variation generated inside the electrooptical display apparatus.
Moreover, when using an internal load as the load connected to the voltage supply line or the common electrode, a large load variation makes it difficult to provide, in the electrooptical display apparatus, the internal load that can reduce the load variation.